Tar sand is composed of a mixture of viscous hydrocarbon compounds, known as bitumen, occupying pore space within rocks such as sandstone, dolomite, and loose sedimentary deposits, with the particles thereof essentially being bitumen in varying amounts adsorbed on sand granules. Deposits of tar sand are found in the ground in many areas of the world, and are removed from the earth through utilization of mining techniques known in the art for subsequent removal and recovery of the bitumen for refining into usable petroleum products.
Current usual methods employed in the removal of bitumen from tar sand are three in number, and include hot water extraction, pyrolysis, and solvent extraction. Hot water extraction involves heating tar sand with steam, hot water, and sodium hydroxide in separation tanks wherein the sand falls to the bottom and the bitumen floats to the top and is then removed for reclamation.
Pyrolysis consists of partial combustion of the tar sand to decompose the bitumen molecules into gases and liquids for subsequent recovery and refinement.
The solvent extraction method involves mixing tar sand with a solvent in which bitumen is soluble, and then removing the solvent-plus-bitumen from the remaining sand for subsequent recovery of the bitumen. For this method to be successful, however, a considerable length of time is required for the solvent to be in contact with the tar sand in order to remove a beneficial amount of bitumen, thus producing a costly low throughput of material and low reclamation of bitumen per unit of time even when stirring, refluxing, or other such mechanical means are utilized.
The invention disclosed herein, however, discloses a method of removing bitumen from tar sand in a relatively short period of time to yield a relatively high, and thus efficient, throughput of material and resulting reclamation potential of bitumen per unit of time. The method comprises submerging tar sand in a sufficient amount of a circulating solvent in which the bitumen is soluble, and, while the tar sand is so submerged, sonicating within the solvent with a sufficient amount of sonic energy to break apart any connections between sand granules and to remove bitumen from the said granules to permit the bitumen so removed to go into solution in the solvent for subsequent removal of the solvent-plus-bitumen and recovery of the bitumen therefrom.